BuddyPress Notification

I want to put some notification things, something like Facebook notification. So when someone Post any updates in BP Activity page, others will get the notification as ‘User1 has updated a post’ or if somebody has unlocked something, regardless WP-Achievement plugin, then there should be notification on the top bar.

I hope there would be a function or hook so that i can trigger my own notification wherever i want

and the otherSite is http://ux.arrancr.co.uk/, BuddyPress 1.6.2 with theme iTheme2 from <http://themify.me/&gt;

The problem I am facing is that when I update post on my any site’s Activity page then other registered users are not getting any notification like facebook does. Please register yourselves and have a look. That is all!